Parallel conductors 3.4.3
Parallel conductors 3.4.3
Can conductors within a multi core cable smaller than 4mm², be used in parallel? Such as a 2.5mm² 4c+e used with two sets of parallel conductors.
3.4.3 says "Current-carrying capacities for circuits comprising parallel multi-core cables or groups of single-core cables...."
To me, that means paralleling one multi core cable with another multi core cable.
I believe that the clause shouldn't have any relevance for conductors within a cable.
I'm sure I've seen this done within large multi cores, where some cores are paralleled to reduce voltage drop on long runs.
3.4.3 says "Current-carrying capacities for circuits comprising parallel multi-core cables or groups of single-core cables...."
To me, that means paralleling one multi core cable with another multi core cable.
I believe that the clause shouldn't have any relevance for conductors within a cable.
I'm sure I've seen this done within large multi cores, where some cores are paralleled to reduce voltage drop on long runs.
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Re: Parallel conductors 3.4.3
Looking at "(a) cables shall be not less than 4mm2....."DougP wrote: ↑Fri Apr 17, 2020 10:15 amCan conductors within a multi core cable smaller than 4mm², be used in parallel? Such as a 2.5mm² 4c+e used with two sets of parallel conductors.
3.4.3 says "Current-carrying capacities for circuits comprising parallel multi-core cables or groups of single-core cables...."
To me, that means paralleling one multi core cable with another multi core cable.
I believe that the clause shouldn't have any relevance for conductors within a cable.
I'm sure I've seen this done within large multi cores, where some cores are paralleled to reduce voltage drop on long runs.
the way I read it 2.5mm2 would not be allowed to be paralleled up
Re: Parallel conductors 3.4.3
Except that the requirements of the clause should only apply, when the whole clause is applicable to the situation.
So if the conductors being paralleled aren't included in the clause, then none of the requirements of the clause apply?
Re: Parallel conductors 3.4.3
The conductors of a single multicore cable would be a group of single-core cables; so the way I read it parallelling 2.5s within a single multicore is forbidden, same as for multiple multicores.
Reading it any other way is basically ignoring the underlying theory.
That said, I believe this clause would be better if it referred to "conductors" instead of "cables"
Reading it any other way is basically ignoring the underlying theory.
That said, I believe this clause would be better if it referred to "conductors" instead of "cables"
Re: Parallel conductors 3.4.3
Except that it does say "cables". Multiple times. And conductors, zero times.
And as you keep telling us, read the words that are written, and/or the words that aren't used are just as important.
(going off memory, not direct quotes)
1.4.17
1.4.19
1.4.31
?
And as you keep telling us, read the words that are written, and/or the words that aren't used are just as important.
(going off memory, not direct quotes)
1.4.17
1.4.19
1.4.31
?
Re: Parallel conductors 3.4.3
Note that in 1.417 (2007+A1+A2), definition of "cable" includes "a single cable core";
and 1.4.19 "cable core" is any "conductor" with its insulation.
So any individual cable core within a multicore cable is itself a cable.
and 1.4.19 "cable core" is any "conductor" with its insulation.
So any individual cable core within a multicore cable is itself a cable.
Re: Parallel conductors 3.4.3
Ok, I guess we could discuss the words for quite some time. To me, it doesn't seem to be the intention of the clause though.
So back in reality, what's the problem with paralleling two pairs smaller than 4mm² in a 4 core conductor?
So back in reality, what's the problem with paralleling two pairs smaller than 4mm² in a 4 core conductor?
Re: Parallel conductors 3.4.3
The outcomes for 4 mm2 min conductor parallel limitation comes from the IEC 60364.
The outcome required is the distribution of the total current evenly between all cable cores in parallel so they must have the same impedance for this to occur. This means the conductor material, cross-sectional area and the length must also be the same.
The IEC does not consider that this does happen reliably in conductors under 4 mm2 so do not permit paralleling of under 4 mm2
The outcome required is the distribution of the total current evenly between all cable cores in parallel so they must have the same impedance for this to occur. This means the conductor material, cross-sectional area and the length must also be the same.
The IEC does not consider that this does happen reliably in conductors under 4 mm2 so do not permit paralleling of under 4 mm2
Re: Parallel conductors 3.4.3
That's interesting thanks Pluto!pluto wrote: ↑Sat Apr 18, 2020 12:12 pmThe outcomes for 4 mm2 min conductor parallel limitation comes from the IEC 60364.
The outcome required is the distribution of the total current evenly between all cable cores in parallel so they must have the same impedance for this to occur. This means the conductor material, cross-sectional area and the length must also be the same.
The IEC does not consider that this does happen reliably in conductors under 4 mm2 so do not permit paralleling of under 4 mm2
Re: Parallel conductors 3.4.3
Interesting
I can understand how those requirements may not be met in separate cables but isn't that more due to the cable runs could end up at different lengths/routes etc?
If they were in the same cable sheath like Doug suggested would that almost guarantee those conditions be met?
I can understand how those requirements may not be met in separate cables but isn't that more due to the cable runs could end up at different lengths/routes etc?
If they were in the same cable sheath like Doug suggested would that almost guarantee those conditions be met?